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Thread: .375 H&H Primer Pressure Signs

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    Default .375 H&H Primer Pressure Signs

    I'm new to loading the .375 H&H, therefore I would appreciate some help evaluating these subtle but noted pressure signs. I think the photo is pretty much self explanatory and the individual cartridges representative of the series as I worked up in powder charge. However, to add a little further information, these were once fired rounds. There were no extraction problems noted and just slight case stretching above the belt as I would expect. The slight blue color around some of the primer pockets is residue from my metal cleaner, not sign of leakage. What's noted as a sign of increasing pressure is the obvious flattening and stretching of the primer as I went up in powder charge. Should I be concerned and back-off from the maximum recommended powder charge of 77 grains of RL 15 because of these pressure signs? Load data is from the #4 Barnes Reloading Manual.

    Thanks,

    Eric
    Attached Thumbnails Attached Thumbnails _375-Primer-Pressure.jpg  

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    Quote Originally Posted by ekberger View Post
    I'm new to loading the .375 H&H, therefore I would appreciate some help evaluating these subtle but noted pressure signs. I think the photo is pretty much self explanatory and the individual cartridges representative of the series as I worked up in powder charge. However, to add a little further information, these were once fired rounds. There were no extraction problems noted and just slight case stretching above the belt as I would expect. The slight blue color around some of the primer pockets is residue from my metal cleaner, not sign of leakage. What's noted as a sign of increasing pressure is the obvious flattening and stretching of the primer as I went up in powder charge. Should I be concerned and back-off from the maximum recommended powder charge of 77 grains of RL 15 because of these pressure signs? Load data is from the #4 Barnes Reloading Manual.

    Thanks,

    Eric
    Eric,
    I run the same load, only difference being I use CCI 250's My first question after seeing these is "how did they group secondly what was the velocity"? If your 77 load grouped the best I would be happy with it understanding there are no other pressure signs. My load does not show as much flattening as yours did but that can also be the actual rifle being different and/or me using different primers.

    Max load does not have to be "the best". Your particular rifle just might like things cut down a bit. With the looks of those primers I would just be looking for what load grouped the best.

    Hope this helps!

    Will

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    Default .375 H&H Primer Pressure Signs

    Will, yes it helps and thanks for your reply.

    I guess I'm being cautious, because I'm new to this load and saw these signs which I wanted a second opinion on.

    To your questions: Unfortunately I do not have a chronograph so I cannot evaluate the velocity, however, that may have to change. Secondly, the grouping wasn't bad at 50 yards, within 3" unfortunately I can't evaluate that in the manner in which I'd like to because I'm shooting this gun with open sights and this was the first time out of the box. Quite frankly, I don't know what I can expect in terms of groups shooting this gun at this range without a scope. Maybe I'm just making excuses for my inexperience.

    I'm in the process of putting together some new loads under the maximum that you saw here and will try to get some more data.

    Again, many thanks for the comments.

    Eric

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    Default new also

    I'm only about 500rounds into reloading myself so take this for what it's worth, but I have read a ton of books, so am wondering,

    As that sure looks like the beginning of "Cratering Primer" at 75gr and progresses at 77, how many pressure signs are needed to indicate high pressure?
    Looks like you've got one going on there pretty clearly, so should stop back at 73 or 74gr right? What were the groups like at 73?
    I'd think even with open sights at that range you could get a good feel for some loads tightening up versus others. Keep working with what you have, but I did get a good ProChrono off Midway website for $120, works well, opens up a Whole new bunch of Statistics to obsess about, still learning like crazy here

    Thanks for posting pics, easier to learn from everyone's opinions here
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    Quote Originally Posted by kodiakrain View Post
    . . . how many pressure signs are needed to indicate high pressure?
    Let me warn that you can have excessively high pressure with no visible pressure signs. In fact, most of the so called pressure signs may not arise until after maximum pressure has been surpassed. That said, if you have a single indication (any type) of excessive pressure I would take that very seriously until you discern the cause of the indicator. For example stiff bolt lift, even with mild ammunition, can be caused by poor mating of bolt lugs and the receiver. Once the lugs are properly mated to the mortises the bolt lift may resume to normal displaying that the issue was in the firearm not in the ammunition.

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    If I may add that I think the Barnes data is flawed. I wrote them last year and made a call and disused some data with them that I had worked up. The next week they posted a bulletin on their web site resending their Win 748 data for over pressure concerns.

    I'm a fan of the 375 Ruger but I also load the 375H&H for two friends. I have tested with H4350, RL-15, Win760 and Win 748 in the H&H. Keep in mind that Ruger introduced and advertised that they could beat the H&H even with a 20" barrel. The Ruger case has more capacity. Production Hornady ammo is faster than any other production 375H&H ammo.

    Having said all that, look at the Barnes data on the H&H and the Ruger. Barnes data loads the H&H way hotter than the Ruger or any production ammo. I feel that their H&H data is bogus.

    I have had great results and safe loads with 73.5gr of RL-15 with the 270TSX. Your pic of the 77gr charge shows cratering.

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    Default Primer pressure signs

    My thanks to everyone who responded to my initial question on this topic. They have been helpful and instructive to me and hopefully to others. I can now work through this with confidence.

    Eric

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    I should probably keep quiet, but actually, I don't think those primers are badly flattened, including the last one at 77 grains. I don't see any rub marks on the case head either.

    I'm guessing, (from looking at the picture), you are seeing signs of increasing pressure, from one case, to the other as you increase the charge, but not necessarily, excessive pressure.

    Make sure of the data, and you might look at a fired primer. If you have a brim on the closed end of the primer, it's badly flattened.

    But, it's your arse, so if you're not comfortable with the way they look, back off a bit. I doubt it'll make much difference in performance.

    And, I hafta say,,,

    that 1Cor15:19's post is IMPORTANTLY CORRECT. I'm sure of it.

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  9. #9

    Default Just a few suggestions

    with working up a load like this:

    Work up one grain at a time, especially when pressure signs start to show, such as at the 75 grain loading. That leap from 70 to 73 grains is a bit much in my book, even at one manual's starting point.
    I always cross reference at least 3 different sets of loading data when possible, and average out the loads.
    You didn't mention what kind of primer. Since it is up here where colder temps are always possible and especially with such a large load of high density powder, I'd always start with magnum primers, that is Start over again if a magnum primer was not used the first time.
    I would try several different primers to compare pressure signs at the primer.
    I am of the opinion that expansion (not stretch) just above the belt is a better indicator of pressure increase.
    Hope this helps.

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    Barnes data seems a bit high for that combo. Most 260-270 grain bullets max out around 73 grains of RL15. Barnes claims you can run their TSX's higher than conventional bullets, but 77 grains seems excessive.

    I run the same combo with 74 grains or RL15 and it puts the velocity right at 2700 in a 24" barrel and is pretty accurate.

    I would also go up in one grain increments as noted.

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    Quote Originally Posted by TomM View Post
    Barnes data seems a bit high for that combo. Most 260-270 grain bullets max out around 73 grains of RL15. Barnes claims you can run their TSX's higher than conventional bullets, but 77 grains seems excessive.

    I run the same combo with 74 grains or RL15 and it puts the velocity right at 2700 in a 24" barrel and is pretty accurate.

    I would also go up in one grain increments as noted.
    I sent him a sheet on chrony data that I had saved on that load. I ended up at 73.5 of RL-15 running at 2731fps. I had saved the data on loads from 71.0 - 74.5 in .5 increments. In my testing 77gr was unapproachable. Perhaps with colder AK temps and a shorter barrel but not in the 24" tube I was testing.

    Mauserboy, his photos show Federal 215 large rifle magnum primers.

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    Lots of helpful information already posted here...

    I'll simply add that I have been handloading the 375H&H with 270 X's and TSX's for a decade. That is my favorite caliber and bullet for the fall up here. My rifle is a Browning A-Bolt with a 24" Lilja barrel. My load has always been 76grns of RL-15 with CCI magnum primers. The accuracy has been and continues to be excellent. RL-15 is a temperature tolerant powder, so I doubt ambient temperature is a significant factor. My velocities have been in the 2780fps range. I have had no pressure signs of any kind (noted...that may mean nothing), but many of my cases have been used a whole bunch of times, and they keep on working.

    I also say that what works for me may not work for you. There are factors other than simply powder charges that can create excessive pressures.

    Doc

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    Wow,
    Great stuff here. I am actually in the process of reloading for the H&H for the first time. I bought a box of 270 gr. TSX's and some R-15 and a Barnes #4 manual. I FL sized and trimmed each case and plan on using fed 215 primers like the Barnes manual recommends. I will weigh each load on an electronic scale and start at the 70 gr. charge and work up .5 gr until I approach just under max. I am shooting an older interarms whitworth that I had a competent gunsmith give the thumbs up on. I won't shoot these until the weather matches fall temps. But I will post my results. Again, thanks to you guys for being generous with your past experiences. I am open for any other suggestions.
    Mike

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    Although the primer is starting to indicate high pressure the case isn't. It's possible the firing pin to firing pin hole size is allowing premature cratering. I would try a different primer and work up again at 1 gr increments. You are not getting excessive primer fillout on the outer edge of the primer. So although you are probably close to max at 77gr, I would be looking for accuracy from 72grs up to about 76gr and go with what shoots the best in that range if a different primer doesn't stop the cratering. Good luck.

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    Default .375 lH&H oading

    I don't know what you are hunting but if you need to load a .375 H&H to maximum to kill it- you need a bigger gun! I view all my guns that way except my .500 S&W cause they don't make one bigger - yet! Actually, like the .375 the .500 has plenty of punch at any normal loads - I don't know nor care what the maximum load is.

    Concentrate on what what shoots well in the gun - it probably won't be at the maximum load. A few fps isn't going to make any real differecnce anywhere. Just because it is a "magnum" does not mean it has to be pused to the limit.

    Stop worrying, work up a good accurate load, and start practicing esp. off hand. A .375 isn't that difficult to master but it does take a bit of practice like anything else. Enjoy!


    Quote Originally Posted by kman45 View Post
    Wow,
    Great stuff here. I am actually in the process of reloading for the H&H for the first time. I bought a box of 270 gr. TSX's and some R-15 and a Barnes #4 manual. I FL sized and trimmed each case and plan on using fed 215 primers like the Barnes manual recommends. I will weigh each load on an electronic scale and start at the 70 gr. charge and work up .5 gr until I approach just under max. I am shooting an older interarms whitworth that I had a competent gunsmith give the thumbs up on. I won't shoot these until the weather matches fall temps. But I will post my results. Again, thanks to you guys for being generous with your past experiences. I am open for any other suggestions.
    Mike
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    I have a 375H&H but little experience reloading for it but have reloaded for 50 years, not all of them with the care, concern, resources or experience of today. These discussions including the primer photo as very graphic representation of the results of various pressures is great. Personally I think the 77 shows too much flattening onto the bolt face and into the rim grove to be a load I'd shoot as a standard load. On the other hand maybe I'm looking too much at the flattening and not enough at the firingpin cratering.
    Shown is one of my most accurate varmint load for the 270 WSM which is over Sierra manual but I worked this up carefully based on several others who use this exact load: 90. Gr Sierra, 68 gr IMR 4350. Here's a photo of the primer on this load. It has less flattening but more cratering. This wasnfired in a new Winchester Extreme Weather M70.
    What do you think?



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    I don't think any of the primers on the 375 H&H cases is excessive......having said that I must also say that I don't have much faith in using primer appearance as a pressure indicator. I have run pressure equipment that indicated loads well within the norm for pressure with flattened and cratered primers, and just the opposite, pressures of 10 to 15% over rated norms with no flattening or cratering.

    Generally, while looking at those primers and case head signature I see scrub marks at 73.0 grains. Something about that makes me call it at 73.0 or 74.0. I have loaded a lot of 270 grain Barnes TSX with 74.0 grains of RL-15. I have some notes with some guns as 74.0 grains being too much. Every gun is different and with that long skinny H&H case, a little can make a big difference. I load by velocity in the H&H and with 24" guns, 300 grains at 2560 fps and 270 grains at 2750. The Barnes #4 manual does list for the 270 grain TSX and RL-15 at 77.0 grains as max. The Barnes #3 manual list 76.0 grains of RL-15 as max with the 270 grain XFB. Both those loads show a velocity of about 2775 to 2800 fps.......hmmmm prudence is wisdom.

    An interesting tid bit, from that same Barnes #4 manual it list 73.5 grains as a max load for the 375 RUGER with that same 270 grain TSX bullet......The Ruger is a larger case so that tells me the H&H data is very likely flawed and should be no more than 74.0 grains as max. Both were 24" barrels.
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    Quote Originally Posted by Murphy View Post
    An interesting tid bit, from that same Barnes #4 manual it list 73.5 grains as a max load for the 375 RUGER with that same 270 grain TSX bullet......The Ruger is a larger case so that tells me the H&H data is very likely flawed and should be no more than 74.0 grains as max. Both were 24" barrels.
    A agree 100% with Murphy's observation. I actually stopped at 73.5gr of RL-15 as noted in my earlier post. I even called Barnes about this very same topic last year and they stand by their data, strange...

    The 375 Ruger was designed from the onset to out preform the 375 H&H so why did Barnes get it backwards?

    As Murphy points out, prudence is wisdom, be carefull.

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